The study is designed to test the heterogeneous responses of different patients with glucose 6 phosphatase deficiency in hydrolyzing and absorbing glucose when administered raw starches from different sources. When divergent results are obtained, family studies are pursued. Further, the results obtained are supplied to the management of the patients with glucose 6 phosphatase deficiency. Using cooked and uncooked starches which have been tested in vivo, we have measured amylase in vitro with cooked and uncooked starches using commercial amylase and patients sera. We did not see the 1:1 correlation of in vivo and in vitro results expected.